ssh-add ~/.ssh/id_rsa
ssh-add ~/.ssh/id_rsa_PERSONAL
printf "yay it works!" > ~/lol.txt

more info: http://stackoverflow.com/questions/22842016/launch-shell-script-on-login-in-mac-os-os-x
on a new machine, you must create a plist file like the one below and place it in
~/Library/LaunchAgents/
ex: ~/Libary/LaunchAgents/startscripts.plist
after you create the plist, run
launchctl load ~/Library/LaunchAgents/pathto.plist
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>NAMEOFSCRIPTS</string>
    <key>ProgramArguments</key>
    <array>
          <!-- YOUR LITERAL SCRIPT PATH HERE -->
        <string>/Users/ccummings/script.sh</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
</dict>
</plist>